1. Field of the Invention
The present invention relates to a viscous fluid heat generator which heats a heat medium such as an engine coolant with heat generated by shearing viscous fluid. The viscous fluid heat generator is used, for example, as a heat source for a heater mounted on an automotive vehicle.
2. Description of Related Art
A heat generator which generates heat by shearing viscous fluid contained in a small space is disclosed, for example, in JP-A-3-57877. The heat generated is used for heating an engine coolant. A rotor of the heat generator disclosed therein is rotated by an engine through an electromagnetic clutch which connects or disconnects rotating force of the engine to the rotor. That is, rotation of the rotor is shut off when heat generation is not required. Because the electromagnetic clutch is used, the heat generator disclosed therein becomes large in size and heavy in weight, resulting in a high cost. Therefore, it is desirable to eliminate the clutch. If the clutch is eliminated and the rotor rotates all the time, the engine power to rotate the rotor is always consumed even when it is not required to generate heat. Especially, a large torque for starting the heat generator is necessary.